Some cleanup:

1. Add default options to some switch statements (stuff flagged by static code analysis)
2. Remove unnecessary imports
3. Remove M3U8Element class; it isn't necessary.  It's just a dumb wrapper for LoadForDocumentElement; no point in making life complicated.
Update HTTPHLSNetStream to listen for http-error codes (e.g. 403s); old versions of OSMF will never return these, so it's a no-op.  The new version of strobe I'm working on _will_ possibly send on these errors in the 400+ range, and it correctly handles these.  For instance, there is no point in retrying on a 400-error, so we don't both with the wasteful (and pointless) retry logic.
Fix bug: need to check for isNaN() on the httpCode.
Another try...move int outside the check for m3u8 since it might be looking for either that, or a .ts segment.  In either instance, something like a 400 error is a done deal.
Merge pull request #28 from jnoring/master

Some code cleanup.